The hardest hit of the West African nations facing the deadly Ebola outbreak, Liberia, has set a national goal of recording no new cases by Christmas, December 25.

President Ellen Johnson Sirleaf said in a nationwide radio address Sunday that her country's path to recovery will be difficult. She said Liberia's health care system must be better prepared for any future disease epidemic, with sharp improvements also needed in the country's economy and governance.

She shifted several cabinet officials, saying it was necessary to appoint a team of officials "that is understanding of the prevailing challenges."

More than 2,800 of West Africa's 5,165 Ebola deaths have been recorded in Liberia.

Also Sunday, U.S. health officials said travelers from Mali will be subject to the same screening and monitoring as people arriving from Liberia, Sierra Leone and Guinea. That includes taking arriving travelers' temperatures and questioning them about their health and possible exposure to the Ebola virus.

Although Mali is not suffering from a widespread Ebola outbreak, there have been a number of confirmed cases there in recent days.

Meanwhile, in the U.S., authorities reported that a surgeon, Doctor Martin Salia, who contracted Ebola while working in Sierra Leone, is "extremely ill."

Salia, a Sierra Leone national who lives in the United States, is being treated at a hospital in the central U.S. state of Nebraska.